In previous articles, we found out that neither solar energy will be able to satisfy the needs of humanity (due to the rapid breakdown of batteries and their cost), nor thermonuclear energy (since even after achieving a positive energy output at experimental reactors, a fantastic amount remains problems on the way to commercial use). What remains?

For more than a hundred years, despite all the progress of mankind, the bulk of electricity is obtained from the banal combustion of coal (which is still the source of energy for 40.7% of the world’s generating capacity), gas (21.2%), petroleum products (5.5%) and hydropower (another 16.2%, in total all this is 83.5% of).

What remains is nuclear power, with conventional thermal neutron reactors (requiring rare and expensive U-235) and reactors with fast neutrons(which can process natural U-238 and thorium in a "closed fuel cycle").

What is this mythical “closed fuel cycle”, what are the differences between fast and thermal neutron reactors, what designs exist, when can we expect happiness from all this and of course - the issue of safety - under the cut.

About neutrons and uranium

We were all told at school that U-235, when a neutron hits it, divides and releases energy, and another 2-3 neutrons are released. In reality, of course, everything is somewhat more complicated, and this process strongly depends on the energy of this initial neutron. Let's look at the graphs of the cross section (=probability) of the neutron capture reaction (U-238 + n -> U-239 and U-235 + n -> U-236), and the fission reaction for U-235 and U-238 depending on energy (=speed) of neutrons:

As we can see, the probability of capturing a neutron with fission for U-235 increases with decreasing neutron energy, because in conventional nuclear reactors neutrons are “slowed down” in graphite/water to such an extent that their speed becomes the same order as the speed of thermal vibration of atoms in the crystal lattice (hence the name - thermal neutrons). And the probability of fission of U-238 by thermal neutrons is 10 million times less than U-235, which is why it is necessary to process tons of natural uranium in order to pick up U-235.

Someone looking at the bottom graph might say: Oh, great idea! Let's fry cheap U-238 with 10 MeV neutrons - it should result in a chain reaction, because that's where the graph of the cross section for fission goes up! But there is a problem - the neutrons released as a result of the reaction have an energy of only 2 MeV or less (on average ~1.25), and this is not enough to launch a self-sustaining reaction on fast neutrons in U-238 (either more energy is needed, or more neutrons flew out of every division). Eh, humanity is unlucky in this universe...

However, if a self-sustaining reaction on fast neutrons in U-238 was so easy, there would be natural nuclear reactors, as was the case with U-235 in Oklo, and accordingly U-238 would not be found in nature in the form of large deposits.

Finally, if we abandon the “self-sustaining” nature of the reaction, it is still possible to divide U-238 directly to produce energy. This is used, for example, in thermonuclear bombs - the 14.1MeV neutrons from the D+T reaction divide the U-238 in the bomb shell - and thus the power of the explosion can be increased almost free of charge. Under controlled conditions, there remains a theoretical possibility of combining fusion reactor and a blanket (shell) of U-238 - to increase the energy of thermonuclear fusion by ~10-50 times due to the fission reaction.

But how do you separate U-238 and thorium in a self-sustaining reaction?

Closed fuel cycle

The idea is as follows: let's look not at the fission cross section, but at the capture cross section: With a suitable neutron energy (not too low, and not too high), U-238 can capture a neutron, and after 2 decays it can become plutonium-239:

From spent fuel, plutonium can be isolated chemically to make MOX fuel (a mixture of plutonium and uranium oxides) which can be burned both in fast reactors and in conventional thermal ones. The process of chemical reprocessing of spent fuel can be very difficult due to its high radioactivity, and has not yet been completely solved and practically not worked out (but work is underway).

For natural thorium - a similar process, thorium captures a neutron, and after spontaneous fission, becomes uranium-233, which is divided in approximately the same way as uranium-235 and is released from spent fuel chemically:

These reactions, of course, also occur in conventional thermal reactors - but due to the moderator (which greatly reduces the chance of neutron capture) and control rods (which absorb some of the neutrons), the amount of plutonium generated is less than that of uranium-235 burned. In order to generate more fissile substances than are burned, you need to lose as few neutrons as possible on the control rods (for example, using control rods made of ordinary uranium), the structure, the coolant (more on this below) and completely get rid of the neutron moderator (graphite or water ).

Due to the fact that the fission cross section for fast neutrons is smaller than for thermal ones, it is necessary to increase the concentration of fissile material (U-235, U-233, Pu-239) in the reactor core from 2-4 to 20% and higher. And the production of new fuel is carried out in cassettes with thorium/natural uranium located around this core.

As luck would have it, if fission is caused by a fast neutron rather than a thermal one, the reaction produces ~1.5 times more neutrons than in the case of fission by thermal neutrons - which makes the reaction more realistic:

It is this increase in the number of generated neutrons that makes it possible to produce a larger amount of fuel than was originally available. Of course, new fuel is not taken from thin air, but is produced from “useless” U-238 and thorium.

About the coolant

As we found out above, water cannot be used in a fast reactor - it slows down neutrons extremely effectively. What can replace it?

Gases: You can cool the reactor with helium. But due to their small heat capacity, it is difficult to cool powerful reactors in this way.

Liquid metals: Sodium, potassium- widely used in fast reactors around the world. The advantages are a low melting point and work at near-atmospheric pressure, but these metals burn very well and react with water. The only operating energy reactor in the world, BN-600, runs on sodium coolant.

Lead, bismuth- used in the BREST and SVBR reactors currently being developed in Russia. Of the obvious disadvantages - if the reactor has cooled below the freezing point of lead/bismuth - heating it is very difficult and takes a long time (you can read about the not obvious ones at the link in the wiki). In general, many technological issues remain on the way to implementation.

Mercury- there was a BR-2 reactor with mercury coolant, but as it turned out, mercury relatively quickly dissolves the structural materials of the reactor - so no more mercury reactors were built.

Exotic: A separate category - molten salt reactors - LFTR - operate on different options fluorides of fissile materials (uranium, thorium, plutonium). 2 “laboratory” reactors were built in the USA at Oak Ridge National Laboratory in the 60s, and since then no other reactors have been implemented, although there are many projects.

Operating reactors and interesting projects

Russian BOR-60- experimental fast neutron reactor, operating since 1969. In particular, it is used to test structural elements of new fast neutron reactors.

Russian BN-600, BN-800: As mentioned above, BN-600 is the only fast neutron power reactor in the world. It has been operating since 1980, still using uranium-235.

In 2014, it is planned to launch a more powerful BN-800. It is already planned to start using MOX fuel (with plutonium), and to begin developing a closed fuel cycle (with processing and burning of produced plutonium). Then there may be a serial BN-1200, but the decision on its construction has not yet been made. In terms of experience in the construction and industrial operation of fast neutron reactors, Russia has advanced much further than anyone else and continues to actively develop.

There are also small operating research fast reactors in Japan (Jōyō), India (FBTR) and China (China Experimental Fast Reactor).

Japanese Monju reactor- the unluckiest reactor in the world. It was built in 1995, and in the same year there was a leak of several hundred kilograms of sodium, the company tried to hide the scale of the incident (hello Fukushima), the reactor was shut down for 15 years. In May 2010, the reactor was finally started up at reduced power, but in August, during a fuel transfer, a 3.3-ton crane was dropped into the reactor, which immediately sank in liquid sodium. It was only possible to get the crane in June 2011. On May 29, 2013, a decision will be made to close the reactor forever.

Traveling wave reactor: Among the well-known unrealized projects is the “travelling wave reactor” - traveling wave reactor, from the TerraPower company. This project was promoted by Bill Gates - so they wrote about it twice on Habré: , . The idea was that the “core” of the reactor consisted of enriched uranium, and around it were U-238/thorium cassettes in which future fuel would be produced. Then, the robot would move these cassettes closer to the center - and the reaction would continue. But in reality, it is very difficult to make all this work without chemical processing, and the project never took off.

On the safety of nuclear energy

How can I say that humanity can rely on nuclear energy - and this after Fukushima?

The fact is that any energy is dangerous. Let us recall the accident at the Banqiao dam in China, which was built, among other things, for the purpose of generating electricity - then 26 thousand people died. up to 171 thousand Human. Accident on Sayano-Shushenskaya HPP- 75 people died. In China alone, 6,000 miners die every year during coal mining, and this does not include the health consequences of inhaling exhaust from thermal power plants.

The number of accidents at nuclear power plants does not depend on the number of power units, because Each accident can only occur once in a series. After each incident, the causes are analyzed and eliminated at all units. So, after the Chernobyl accident, all the units were modified, and after Fukushima, nuclear energy was taken away from the Japanese altogether (however, there are also conspiracy theories - the United States and its allies are expected to have a shortage of uranium-235 in the next 5-10 years).

The problem with spent fuel is directly solved by fast neutron reactors, because In addition to improving waste processing technology, less waste is generated: heavy (actinides), long-lived reaction products are also “burned out” by fast neutrons.

Conclusion

Fast reactors have the main advantage that everyone expects from thermonuclear reactors - the fuel for them will last humanity for thousands and tens of thousands of years. You don’t even need to mine it - it’s already been mined and lies on

Academician F. Mitenkov, scientific director of the Federal State Unitary Enterprise "Experimental Design Bureau of Mechanical Engineering" named after. I. I. Afrikantova (Nizhny Novgorod).

Academician Fyodor Mikhailovich Mitenkov was awarded the Global Energy Prize in 2004 for the development of physical and technical fundamentals and the creation of fast neutron power reactors (see Science and Life No. 8, 2004). The research carried out by the laureate and their practical implementation in the operating reactor plants BN-350, BN-600, the BN-800 under construction and the BN-1800 being designed, open up new things for humanity, promising direction development of nuclear energy.

Beloyarsk NPP with BN-600 reactor.

Academician F. M. Mitenkov at the Global Energy Prize award ceremony in June 2004.

Science and life // Illustrations

Science and life // Illustrations

Schematic diagram fast neutron reactor BN-350.

Schematic diagram of the fast energy reactor BN-600.

The central hall of the BN-600 reactor.

The BN-800 fast neutron reactor has an electrical power of 880 MW and a thermal power of 1.47 GW. At the same time, its design ensures complete safety both during normal operation and in any conceivable accident.

Science and life // Illustrations

Power consumption - the most important indicator, which largely determines the level of economic development, national security and well-being of the population of any country. The growth of energy consumption has always accompanied the development of human society, but it was especially rapid during the twentieth century: energy consumption increased almost 15 times, reaching an absolute value of about 9.5 billion tons of oil equivalent (toe) by its end. The combustion of coal, oil, and natural gas provides about 80% of global energy consumption. In the 21st century, its growth will undoubtedly continue, especially in developing countries, for which economic development and improving the quality of life of the population are inevitably associated with a significant increase in the amount of energy consumed, primarily its most universal type - electricity. By the middle of the 21st century, global energy consumption is projected to double and electricity consumption to triple.

The general trend of growth in energy consumption increases the dependence of most countries on the import of oil and natural gas, intensifies competition for access to energy resources, and creates a threat to global security. At the same time, concern about the environmental consequences of energy production is growing, primarily due to the danger of unacceptable air pollution from emissions of hydrocarbon fuel combustion products.

Therefore, in the not too distant future, humanity will be forced to switch to the use of alternative “carbon-free” energy production technologies that will reliably meet growing energy needs for a long time without unacceptable environmental consequences. However, we have to admit that the currently known renewable energy sources - wind, solar, geothermal, tidal, etc. - due to their potential capabilities cannot be used for large-scale energy production (see "Science and Life" No. 10, 2002 - Note ed.). And the very promising technology of controlled thermonuclear fusion is still at the stage of research and creation of a demonstration nuclear reactor (see "Science and Life" No. 8, 2001, No. 9, 2001 - Note ed.).

According to many experts, including the author of this article, the real energy choice of humanity in the 21st century will be the widespread use of nuclear energy based on fission reactors. Nuclear energy could already now take on a significant portion of the increase in global demand for fuel and energy. Today it provides about 6% of global energy consumption, mainly electrical, where its share is about 18% (in Russia - about 16%).

Several conditions are necessary for the wider use of nuclear energy to become the main source of energy in the current century. First of all, nuclear energy needs to meet the requirements of guaranteed safety for the population and the environment, and natural resources for the production of nuclear fuel must ensure the functioning of “large” nuclear energy for at least several centuries. And, in addition, in terms of technical and economic indicators, nuclear energy should not be inferior to the best energy sources using hydrocarbon fuels.

Let's see how modern nuclear energy meets these requirements.

On guaranteed safety of nuclear energy

Since its inception, the safety issues of nuclear energy have been considered and quite effectively resolved systematically and on a scientific basis. However, during the period of its formation, emergencies did arise with unacceptable releases of radioactivity, including two large-scale accidents: at the Three Mile Island nuclear power plant (USA) in 1979 and at Chernobyl nuclear power plant(USSR) in 1986. In this regard, the global community of scientists and nuclear specialists, under the auspices of the International Atomic Energy Agency (IAEA), has developed recommendations, compliance with which virtually eliminates unacceptable impacts on the environment and the population in the event of any physically possible accidents at nuclear power plants. They, in particular, provide: if the design does not reliably prove that a meltdown of the reactor core is excluded, the possibility of such an accident must be taken into account and it must be proven that the physical barriers provided for in the reactor design are guaranteed to exclude unacceptable consequences for the environment. IAEA recommendations included integral part into national nuclear safety standards in many countries around the world. Some engineering solutions that ensure the safe operation of modern reactors are described below using the example of the BN-600 and BN-800 reactors.

Resource base for nuclear fuel production

Nuclear specialists know that the existing nuclear energy technology, based on so-called “thermal” nuclear reactors with a water or graphite neutron moderator, cannot ensure the development of large-scale nuclear energy. This is due to the low efficiency of using natural uranium in such reactors: only the U-235 isotope is used, the content of which in natural uranium is only 0.72%. Therefore, the long-term strategy for the development of “large” nuclear energy involves a transition to advanced closed fuel cycle technology based on the use of so-called fast nuclear reactors and reprocessing of fuel unloaded from reactors of nuclear power plants for the subsequent return of unburned and newly formed fissile isotopes to the energy cycle.

In a “fast” reactor, most of the fission events of nuclear fuel are caused by fast neutrons with an energy of more than 0.1 MeV (hence the name “fast” reactor). At the same time, fission occurs in the reactor not only of the very rare isotope U-235, but also of U-238, the main component of natural uranium (~99.3%), the probability of fission of which in the neutron spectrum of a “thermal reactor” is very low. It is fundamentally important that in a “fast” reactor, with each nuclear fission event, a larger number of neutrons are produced, which can be used for the intensive conversion of U-238 into the fissile isotope of plutonium Pu-239. This transformation occurs as a result nuclear reaction:

The neutron-physical features of a fast reactor are such that the process of formation of plutonium in it can have the character of extended breeding, when more secondary plutonium is formed in the reactor than the amount initially loaded burns up. The process of formation of an excess amount of fissile isotopes in a nuclear reactor is called "breeding" (from the English breed - to multiply). This term is associated with the internationally accepted name for fast reactors with plutonium fuel - breeder reactors, or multipliers.

The practical implementation of the breeding process is of fundamental importance for the future of nuclear energy. The fact is that such a process makes it possible to almost completely use natural uranium and thereby increase the “yield” of energy from each ton of mined natural uranium by almost a hundred times. This opens the way to virtually inexhaustible fuel resources of nuclear energy for a long historical perspective. Therefore, it is generally accepted that the use of breeders is necessary condition creation and operation of large-scale nuclear energy.

After the fundamental possibility of creating fast breeder reactors was realized in the late 1940s, intensive research into their neutronic characteristics and the search for appropriate engineering solutions began around the world. In our country, the initiator of research and development on fast reactors was Academician of the Ukrainian Academy of Sciences Alexander Ilyich Leypunsky, who until his death in 1972 was scientific supervisor Obninsk Physics and Energy Institute (PEI).

The engineering difficulties of creating fast reactors are associated with a number of inherent features. These include: high energy density of fuel; the need to ensure its intensive cooling; high operating temperatures of the coolant, reactor structural elements and equipment; radiation damage to structural materials caused by intense irradiation with fast neutrons. To solve these new scientific and technical problems and develop the technology of fast reactors, it was necessary to develop a large-scale research and experimental base with unique stands, as well as the creation in the 1960-1980s of a number of experimental and demonstration power reactors of this type in Russia, USA, France, UK and Germany. It is noteworthy that in all countries sodium was chosen as the cooling medium - coolant - for fast reactors, despite the fact that it reacts actively with water and steam. The decisive advantages of sodium as a coolant are its exceptionally good thermophysical properties (high thermal conductivity, high heat capacity, high boiling point), low energy consumption for circulation, reduced corrosive effect on the structural materials of the reactor, and the relative ease of its cleaning during operation.

The first domestic demonstration fast neutron power reactor BN-350 with a thermal power of 1000 MW was put into operation in 1973 on the eastern coast of the Caspian Sea (see "Science and Life" No. 11, 1976 - Note ed.). It had a loop heat transfer scheme traditional for nuclear energy and a steam turbine complex for converting thermal energy. Part of the reactor's thermal power was used to generate electricity, the rest was used for desalination sea ​​water. One of distinctive features diagrams of this and subsequent reactor installations with sodium coolant - the presence of an intermediate heat transfer circuit between the reactor and the steam-water circuit, dictated by safety considerations.

The BN-350 reactor plant, despite the complexity of its technological scheme, successfully operated from 1973 to 1988 (five years longer than the design time) as part of the Mangyshlak Energy Plant and the seawater desalination plant in Shevchenko (now Aktau, Kazakhstan).

The large branching of the sodium circuits in the BN-350 reactor caused concern, since in the event of an emergency depressurization, a fire could occur. Therefore, without waiting for the launch of the BN-350 reactor, the USSR began designing a more powerful fast reactor BN-600 of an integral design, in which there were no large-diameter sodium pipelines and almost all of the radioactive sodium in the primary circuit was concentrated in the reactor vessel. This made it possible to almost completely eliminate the risk of depressurization of the first sodium circuit, reduce the fire danger of the installation, and increase the level of radiation safety and reliability of the reactor.

The BN-600 reactor plant has been operating reliably since 1980 as part of the third power unit of the Beloyarsk NPP. Today it is the most powerful fast neutron reactor operating in the world, which serves as a source of unique operational experience and a basis for full-scale testing of advanced structural materials and fuel.

All subsequent projects of this type of reactor in Russia, as well as most commercial fast reactor projects developed abroad, use an integral design.

Ensuring the safety of fast reactors

Already during the design of the first fast neutron power reactors great attention paid attention to safety issues both during their normal operation and during emergency situations. The search directions for appropriate design solutions were determined by the requirement to exclude unacceptable impacts on the environment and population through the internal self-protection of the reactor and the use of effective systems for localizing potential accidents that limit their consequences.

The self-defense of a reactor is based primarily on the action of negative feedback, stabilizing the process of fission of nuclear fuel with increasing temperature and power of the reactor, as well as on the properties of the materials used in the reactor. To illustrate the inherent safety of fast reactors, we will point out some of their features associated with the use of sodium coolant in them. Heat The boiling point of sodium (883oC under normal physical conditions) makes it possible to maintain a pressure close to atmospheric in the reactor vessel. This simplifies the design of the reactor and increases its reliability. The reactor vessel is not subjected to large mechanical loads during operation, so its rupture is even less likely than in existing pressurized water reactors, where it belongs to the hypothetical class. But even such an accident in a fast reactor does not pose a danger from the point of view of reliable cooling of nuclear fuel, since the vessel is surrounded by a sealed safety casing, and the volume of possible sodium leakage into it is insignificant. Depressurization of pipelines with sodium coolant in a fast reactor of an integral design also does not lead to dangerous situation. Since the heat capacity of sodium is quite high, even with a complete cessation of heat removal into the steam-water circuit, the temperature of the coolant in the reactor will increase at a rate of approximately 30 degrees per hour. During normal operation, the coolant temperature at the reactor outlet is 540oC. A significant margin of temperature before sodium boils provides a reserve of time sufficient to take measures to limit the consequences of such an unlikely accident.

In the design of the BN-800 reactor, which uses the basic engineering solutions of the BN-600, additional measures have been taken to ensure that the reactor's integrity is maintained and that there are no unacceptable impacts on the environment, even in the event of a hypothetical, extremely unlikely accident involving a meltdown of the reactor core.

Control panel of the BN-600 reactor.

Long-term operation of fast reactors has confirmed the sufficiency and effectiveness of the provided safety measures. Over the 25 years of operation of the BN-600 reactor, there were no accidents with excess releases of radioactivity, no exposure of personnel, and especially the local population. Fast reactors have demonstrated high operational stability and are easy to control. Sodium coolant technology has been mastered, which effectively neutralizes its fire hazard. Personnel confidently detect leaks and sodium combustion, and reliably eliminate their consequences. IN last years More and more wide application in fast reactor projects, systems and devices are found that can transfer the reactor to a safe state without personnel intervention or external energy supply.

Technical and economic indicators of fast reactors

Features of sodium technology, increased safety measures, and a conservative choice of design solutions for the first reactors - BN-350 and BN-600 - became the reasons for their higher cost compared to water-cooled reactors. However, they were created mainly to test the performance, safety and reliability of fast reactors. This problem was solved by their successful operation. When creating the next reactor installation - BN-800, intended for mass use in nuclear energy, more attention was paid to technical and economic characteristics, and as a result, in terms of specific capital costs, it was possible to significantly approach VVER-1000 - the main type of domestic slow-neutron power reactors.

By now it can be considered established that fast reactors with sodium coolant have great potential for further technical and economic improvement. The main directions for improving their economic characteristics while simultaneously increasing the level of safety include: increasing the unit power of the reactor and the main components of the power unit, improving the design of the main equipment, switching to supercritical steam parameters in order to increase the thermodynamic efficiency of the thermal energy conversion cycle, optimizing the system for handling fresh and spent fuel, increasing the burnup of nuclear fuel, creating a core with high internal coefficient reproduction rate (CR) - up to 1, increasing service life to 60 years or more.

Improvement individual species equipment, as shown by design studies carried out at OKBM, can have a very significant impact on improving the technical and economic indicators of both the reactor plant and the power unit as a whole. For example, studies to improve the refueling system of the promising BN-1800 reactor have shown the possibility of significantly reducing the metal consumption of this system. Replacing modular steam generators with cased ones of an original design can significantly reduce their cost, as well as the area, volume and material consumption of the steam generator compartment of the power unit.

The effect of reactor power and technological improvement of equipment on metal consumption and the level of capital costs can be seen from the table.

Improving fast reactors will naturally require some effort on the part of industrial enterprises, scientific and design organizations. Thus, to increase the burnup of nuclear fuel, it is necessary to develop and master the production of structural materials for the reactor core that are more resistant to neutron irradiation. Work in this direction is currently underway.

Fast reactors can be used for more than just energy. High-energy neutron fluxes are capable of effectively “burning” the most dangerous long-lived radionuclides formed in spent nuclear fuel. This is of fundamental importance for solving the problem of managing radioactive waste from nuclear power. The fact is that the half-life of some radionuclides (actinides) far exceeds the scientifically based stability periods of geological formations, which are considered as final disposal sites for radioactive waste. Therefore, by using a closed fuel cycle with actinide burning and transmutation of long-lived fission products into short-lived ones, it is possible to radically solve the problem of neutralizing nuclear energy waste and greatly reduce the volume of radioactive waste to be buried.

The transfer of nuclear energy, along with “thermal” reactors, to fast breeder reactors, as well as to a closed fuel cycle, will make it possible to create a safe energy technology that fully meets the requirements of the sustainable development of human society.

Many experts today believe that fast neutron reactors are the future of nuclear energy. One of the pioneers in the development of this technology is Russia, where the BN-600 fast neutron reactor at the Beloyarsk NPP has been operating for 30 years without serious incidents, the BN-800 reactor is being built there, and the creation of a commercial BN-1200 reactor is planned. France and Japan have experience in operating fast neutron nuclear power plants, and plans to build fast neutron nuclear power plants in India and China are being considered. The question arises: why are there no practical programs for the development of fast neutron energy in a country with a very highly developed nuclear energy industry - the USA?

In fact, there was such a project in the USA. We are talking about the Clinch River Breeder Reactor project (in English - The Clinch River Breeder Reactor, abbreviated as CRBRP). The goal of this project was to design and build a sodium fast reactor, which was to be a demonstration prototype for the next class of similar American reactors called LMFBR (short for Liquid Metal Fast Breeder Reactors). At the same time, the Clinch River reactor was conceived as a significant step towards the development of liquid metal fast reactor technology for the purpose of their commercial use in the electric power industry. The location of the Clinch River reactor was to be an area of ​​6 km 2, administratively part of the city of Oak Ridge in Tennessee.

The reactor was supposed to have a thermal power of 1000 MW and an electrical power in the range of 350-380 MW. The fuel for it was to be 198 hexagonal assemblies assembled in the shape of a cylinder with two fuel enrichment zones. The interior of the reactor was to consist of 108 assemblies containing plutonium enriched to 18%. They were to be surrounded by an outer zone consisting of 90 assemblies with plutonium enriched to 24%. This configuration should provide best conditions for heat dissipation.

The project was first presented in 1970. In 1971, US President Richard Nixon established this technology as one of the nation's top research and development priorities.

What prevented its implementation?

One of the reasons for this decision was the ongoing escalation of project costs. In 1971, the US Atomic Energy Commission determined that the project would cost about $400 million. The private sector has pledged to finance most of the project, committing $257 million. In subsequent years, however, the cost of the project jumped to 700 million. As of 1981, a billion dollars of budget funds had already been spent, despite the fact that the cost of the project was estimated at that time at 3 - 3.2 billion dollars, not counting another billion , which was necessary for the construction of a plant for the production of generated fuel. In 1981, a congressional committee uncovered cases of various abuses, which further increased the cost of the project.

Before the decision to close, the cost of the project was already estimated at $8 billion.

Another reason was the high cost of building and operating the breeder reactor itself to produce electricity. In 1981, it was estimated that the cost of building a fast reactor would be twice that of a standard light water reactor of the same power. It was also estimated that for the breeder to be economically competitive with conventional light water reactors, the price of uranium would have to be $165 per pound, when in reality the price was then $25 per pound. Private generating companies did not want to invest in such a risky technology.

Another serious reason for curtailing the breeder program was the threat possible violation non-proliferation regime, since this technology produces plutonium, which can also be used for the production of nuclear weapons. Due to international concerns over nuclear proliferation issues, in April 1977, US President Jimmy Carter called for an indefinite delay in the construction of commercial fast reactors.

President Carter was generally a consistent opponent of the Clinch River project. In November 1977, after vetoing a bill to continue funding, Carter said it would be "prohibitively expensive" and "become technically obsolete and economically unfeasible once completed." In addition, he stated that fast reactor technology in general is futile. Instead of pouring resources into the fast neutron demonstration project, Carter proposed instead "spending money on improving the safety of existing nuclear technologies."

The Clinch River Project was resumed after Ronald Reagan took office in 1981. Despite growing opposition from Congress, he overturned his predecessor's ban and construction resumed. However, on October 26, 1983, despite the successful progress of construction work, the US Senate by a majority (56 to 40) called for no further funding for construction and the site was abandoned.

Once again, it was remembered quite recently, when the project of a low-power mPower reactor began to be developed in the USA. The site of the planned construction of the Clinch River Nuclear Power Plant is being considered as the site for its construction.

Fast neutron reactor.

In the structure of large-scale nuclear energy important role allocated to fast neutron reactors with a closed fuel cycle. They make it possible to increase the efficiency of using natural uranium by almost 100 times and, thereby, remove restrictions on the development of nuclear energy from outside natural resources nuclear fuel.
There are currently about 440 nuclear reactors operating in 30 countries around the world, which provide about 17% of all electricity generated in the world. In industrialized countries, the share of “nuclear” electricity is, as a rule, at least 30% and is steadily increasing. However, according to scientists, the rapidly growing nuclear energy industry, based on modern “thermal” nuclear reactors used at nuclear power plants in operation and under construction (most of them with VVER and LWR type reactors), will inevitably already in the current century face a shortage of uranium raw materials due to that the fissile element of fuel for these stations is the rare isotope uranium-235.
In a fast neutron reactor (BN), a nuclear fission reaction produces an excess amount of secondary neutrons, the absorption of which in the bulk of uranium, consisting of uranium-238, leads to the intensive formation of new nuclear fissile material plutonium-239. As a result, from each kilogram of uranium-235, along with energy generation, it is possible to obtain more than one kg of plutonium-239, which can be used as fuel in any nuclear power plant reactors instead of rare uranium-235. This physical process, called fuel reproduction, will allow all natural uranium, including its main part - the uranium-238 isotope (99.3% of the total mass of fossil uranium), to be involved in the nuclear energy industry. This isotope in modern thermal neutron nuclear power plants is practically not involved in energy production. As a result, energy production with existing uranium resources and minimal impact on nature could be increased almost 100 times. In this case, atomic energy will be enough for humanity for several millennia.
According to scientists, the joint operation of “thermal” and “fast” reactors in a ratio of approximately 80:20% will provide nuclear energy with the most efficient use uranium resources. At this ratio, fast reactors will produce enough plutonium-239 to operate nuclear power plants with thermal reactors.
An additional advantage of the technology of fast reactors with an excess amount of secondary neutrons is the ability to “burn out” long-lived (with a decay period of up to thousands and hundreds of thousands of years) radioactive fission products, turning them into short-lived ones with a half-life of no more than 200-300 years. Such converted radioactive waste can be securely buried in special storage facilities without disturbing the natural radiation balance of the Earth.

Work in the field of fast neutron nuclear reactors began in 1960 with the design of the first pilot industrial power reactor BN-350. This reactor was launched in 1973 and was successfully operated until 1998.
In 1980, at the Beloyarsk NPP, as part of power unit No. 3, the next, more powerful power reactor BN-600 (600 MW(e)) was put into operation, which continues to operate reliably to this day, being the largest operating reactor of this type in world. In April 2010, the reactor completed its design service life of 30 years with high reliability and safety indicators. Over a long period of operation, the capacity capacity of the power unit is maintained at a stable level high level- about 80%. Unplanned losses less than 1.5%.
Over the past 10 years of operation of the power unit, there has not been a single case of emergency shutdown of the reactor.
There is no release of long-lived gas aerosol radionuclides into the environment. The yield of inert radioactive gases is currently negligible and amounts to<1% от допустимого по санитарным нормам.
The operation of the reactor convincingly demonstrated the reliability of the design measures for the prevention and containment of sodium leaks.
In terms of reliability and safety, the BN-600 reactor turned out to be competitive with serial thermal neutron reactors (VVER).

Figure 1. Reactor (central) hall of BN-600

In 1983, on the basis of the BN-600, the enterprise developed a project for an improved BN-800 reactor for a power unit with a capacity of 880 MW(e). In 1984, work began on the construction of two BN-800 reactors at the Beloyarsk and new South Ural nuclear power plants. The subsequent delay in the construction of these reactors was used to refine the design in order to further improve its safety and improve technical and economic indicators. Work on the construction of BN-800 was resumed in 2006 at the Beloyarsk NPP (4th power unit) and should be completed in 2013.

Figure 2. Fast neutron reactor BN-800 (vertical section)

Figure 3. Model of the BN-800 reactor

The BN-800 reactor under construction has the following important tasks:

• Ensuring operation on MOX fuel.
• Experimental demonstration of key components of a closed fuel cycle.
• Testing in real operating conditions of new types of equipment and improved technical solutions introduced to improve efficiency, reliability and safety.
• Development of innovative technologies for future fast neutron reactors with liquid metal coolant:
• testing and certification of advanced fuels and structural materials;
• demonstration of technology for burning minor actinides and transmuting long-lived fission products, which constitute the most dangerous part of radioactive waste from nuclear energy.

JSC "Afrikantov OKBM" is developing a project for an improved commercial reactor BN-1200 with a power of 1220 MW.

Figure 3. BN-1200 reactor (vertical section)

The following program for the implementation of this project is planned:

• 2010...2016 - development of the technical design of the reactor plant and implementation of the R&D program.
• 2020 - commissioning of the main power unit using MOX fuel and organization of its centralized production.
• 2023…2030 - commissioning of a series of power units with a total capacity of about 11 GW.

Along with the solutions confirmed by the positive operating experience of the BN-600 and included in the BN-800 project, the BN-1200 project uses new solutions aimed at further improving technical and economic indicators and increasing safety.
According to technical and economic indicators:

• increasing the installed capacity utilization factor from the planned value of 0.85 for BN-800 to 0.9;
• gradual increase in burnup of MOX fuel from the achieved level in experimental fuel assemblies of 11.8% t.a. up to the level of 20% t.a. (average burnup ~140 MW day/kg);
• increasing the breeding factor to ~1.2 on uranium-plutonium oxide fuel and to ~1.45 on mixed nitride fuel;
• reduction in specific metal consumption indicators by ~1.7 times compared to BN-800
• increasing the service life of the reactor from 45 years (BN-800) to 60 years.

For safety:

• the probability of severe damage to the core should be an order of magnitude less than the requirements of regulatory documents;
• the sanitary protection zone must be located within the boundaries of the NPP site for any design basis accidents;
• the boundary of the protective measures zone must coincide with the boundary of the NPP site for severe beyond design basis accidents, the probability of which does not exceed 10-7 per reactor/year.

The optimal combination of reference and new solutions and the possibility of expanded fuel reproduction make it possible to classify this project as a fourth generation nuclear technology.

JSC "Afrikantov OKBM" actively participates in international cooperation on fast reactors. It was the developer of the Chinese experimental fast neutron reactor CEFR project and the main contractor for the manufacture of the main equipment of the reactor, participated in the physical and power startup of the reactor in 2011 and is assisting in the development of its power. Currently, an intergovernmental agreement is being prepared for the construction in China of a sodium-cooled demonstration fast reactor (CDFR) based on the BN-800 project with the participation of OKBM and other enterprises of the Rosatom State Corporation.

After the launch and successful operation of the world's first nuclear power plant in 1955, on the initiative of I. Kurchatov, a decision was made to build an industrial nuclear power plant with a channel-type pressurized water reactor in the Urals. Features of this type of reactor include superheating of steam to high parameters directly in the core, which opened up the possibility of using serial turbine equipment.

In 1958, in the center of Russia, in one of the most picturesque corners of the Ural nature, the construction of the Beloyarsk Nuclear Power Plant began. For installers, this station began back in 1957, and since the topic of nuclear power plants was closed in those days, in correspondence and life it was called the Beloyarsk State District Power Plant. This station was started by employees of the Uralenergomontazh trust. Through their efforts, in 1959, a base with a workshop for the production of water and steam pipelines (1 circuit of the reactor) was created, three residential buildings were built in the village of Zarechny, and construction of the main building began.

In 1959, workers from the Tsentroenergomontazh trust appeared at the construction site and were tasked with installing the reactor. At the end of 1959, the site for the construction of the nuclear power plant was relocated from Dorogobuzh, Smolensk region, and installation work was headed by V. Nevsky, the future director of the Beloyarsk NPP. All work on the installation of thermal mechanical equipment was completely transferred to the Tsentroenergomontazh trust.

The intensive period of construction of the Beloyarsk NPP began in 1960. At this time, the installers, along with construction work, had to master new technologies for the installation of stainless pipelines, linings of special rooms and radioactive waste storage facilities, installation of reactor structures, graphite masonry, automatic welding, etc. We learned on the fly from specialists who had already taken part in the construction of nuclear facilities. Having moved from the technology of installation of thermal power plants to the installation of equipment for nuclear power plants, the workers of Tsentroenergomontazh successfully completed their tasks, and on April 26, 1964, the first power unit of the Beloyarsk NPP with the AMB-100 reactor supplied the first current to the Sverdlovsk energy system. This event, along with the commissioning of the 1st power unit of the Novovoronezh NPP, meant the birth of the country's large nuclear power industry.

The AMB-100 reactor was a further improvement in the reactor design of the World's First Nuclear Power Plant in Obninsk. It was a channel-type reactor with higher thermal characteristics of the core. Obtaining steam of high parameters due to nuclear overheating directly in the reactor was a big step forward in the development of nuclear energy. the reactor operated in one unit with a 100 MW turbogenerator.

Structurally, the reactor of the first power unit of the Beloyarsk NPP turned out to be interesting in that it was created virtually without a frame, i.e., the reactor did not have a heavy, multi-ton, durable body, like, say, a water-cooled water-cooled VVER reactor of similar power with a body 11-12 m long , with a diameter of 3-3.5 m, wall and bottom thickness of 100-150 mm or more. The possibility of constructing nuclear power plants with open-channel reactors turned out to be very tempting, since it freed heavy engineering plants from the need to manufacture steel products weighing 200-500 tons. But the implementation of nuclear overheating directly in the reactor turned out to be associated with well-known difficulties in regulating the process, especially in terms of monitoring its progress , with the requirement for precision operation of many instruments, the presence of a large number of pipes of various sizes under high pressure, etc.

The first unit of the Beloyarsk NPP reached its full design capacity, however, due to the relatively small installed capacity of the unit (100 MW), the complexity of its technological channels and, therefore, high cost, the cost of 1 kWh of electricity turned out to be significantly higher than that of thermal stations in the Urals.

The second unit of the Beloyarsk NPP with the AMB-200 reactor was built faster, without great stress in the work, since the construction and installation team was already prepared. The reactor installation has been significantly improved. It had a single-circuit cooling circuit, which simplified the technological design of the entire nuclear power plant. Just like in the first power unit, the main feature of the AMB-200 reactor is the delivery of high-parameter steam directly to the turbine. On December 31, 1967, power unit No. 2 was connected to the network - this completed the construction of the 1st stage of the station.

A significant part of the history of operation of the 1st stage of the BNPP was filled with romance and drama, characteristic of everything new. This was especially true during the period of block development. It was believed that there should be no problems with this - there were prototypes from the AM “First in the World” reactor to industrial reactors for plutonium production, on which basic concepts, technologies, design solutions, many types of equipment and systems, and even a significant part of the technological regimes were tested . However, it turned out that the difference between the industrial nuclear power plant and its predecessors is so great and unique that new, previously unknown problems arose.

The largest and most obvious of them was the unsatisfactory reliability of the evaporation and superheating channels. After a short period of their operation, gas depressurization of fuel elements or coolant leaks appeared with unacceptable consequences for the graphite masonry of reactors, technological operating and repair modes, radiation exposure on personnel and the environment. According to the scientific canons and calculation standards of that time, this should not have happened. In-depth studies of this new phenomenon forced us to reconsider the established ideas about the fundamental laws of boiling water in pipes, since even with a low heat flux density, a previously unknown type of heat transfer crisis arose, which was discovered in 1979 by V.E. Doroshchuk (VTI) and subsequently called the “heat transfer crisis of the second kind.”

In 1968, a decision was made to build a third power unit with a fast neutron reactor at the Beloyarsk NPP - BN-600. The scientific supervision of the creation of BN-600 was carried out by the Institute of Physics and Power Engineering, the design of the reactor plant was carried out by the Experimental Mechanical Engineering Design Bureau, and the general design of the unit was carried out by the Leningrad branch of Atomelectroproekt. The block was built by a general contractor - the Uralenergostroy trust.

When designing it, the operating experience of the BN-350 reactors in Shevchenko and the BOR-60 reactor was taken into account. For the BN-600, a more economical and structurally successful integral layout of the primary circuit was adopted, according to which the reactor core, pumps and intermediate heat exchangers are located in one housing. The reactor vessel, having a diameter of 12.8 m and a height of 12.5 m, was installed on roller supports fixed to the base plate of the reactor shaft. The mass of the assembled reactor was 3900 tons, and the total amount of sodium in the installation exceeded 1900 tons. Biological protection was made of steel cylindrical screens, steel blanks and pipes with graphite filler.

The quality requirements for installation and welding work for the BN-600 turned out to be an order of magnitude higher than those achieved previously, and the installation team had to urgently retrain personnel and master new technologies. So in 1972, when assembling a reactor vessel from austenitic steels, a betatron was used for the first time to control the transmission of large welds.

In addition, during the installation of internal devices of the BN-600 reactor, special requirements for cleanliness were imposed, and all parts brought in and removed from the intra-reactor space were recorded. This was due to the impossibility of further flushing the reactor and pipelines with sodium coolant.

Nikolai Muravyov, who was able to invite him to work from Nizhny Novgorod, where he had previously worked in a design bureau, played a major role in the development of reactor installation technology. He was one of the developers of the BN-600 reactor project, and by that time he was already retired.

The installation team successfully completed the assigned tasks of installing the fast neutron unit. Filling the reactor with sodium showed that the purity of the circuit was maintained even higher than required, since the pour point of sodium, which depends in the liquid metal on the presence of foreign contaminants and oxides, turned out to be lower than those achieved during the installation of the BN-350, BOR-60 reactors in the USSR and nuclear power plants " Phoenix" in France.

The success of the installation teams at the construction of the Beloyarsk NPP largely depended on the managers. First it was Pavel Ryabukha, then the young energetic Vladimir Nevsky came, then he was replaced by Vazgen Kazarov. V. Nevsky did a lot for the formation of a team of installers. In 1963, he was appointed director of the Beloyarsk Nuclear Power Plant, and later he headed Glavatomenergo, where he worked hard to develop the country’s nuclear power industry.

Finally, on April 8, 1980, the power start-up of power unit No. 3 of the Beloyarsk NPP with the BN-600 fast neutron reactor took place. Some design characteristics of the BN-600:

• electrical power – 600 MW;
• thermal power – 1470 MW;
• steam temperature – 505 o C;
• steam pressure – 13.7 MPa;
• gross thermodynamic efficiency – 40.59%.

Special attention should be paid to the experience of handling sodium as a coolant. It has good thermophysical and satisfactory nuclear physical properties, and is well compatible with stainless steels, uranium and plutonium dioxide. Finally, it is not scarce and relatively inexpensive. However, it is very chemically active, which is why its use required solving at least two serious problems: minimizing the likelihood of sodium leakage from circulation circuits and inter-circuit leaks in steam generators and ensuring effective localization and termination of sodium combustion in the event of a leak.

The first task was generally quite successfully solved at the stage of developing equipment and pipeline projects. The integral layout of the reactor turned out to be very successful, in which all the main equipment and pipelines of the 1st circuit with radioactive sodium were “hidden” inside the reactor vessel, and therefore its leakage, in principle, was possible only from a few auxiliary systems.

And although BN-600 is today the largest power unit with a fast neutron reactor in the world, Beloyarsk NPP is not one of the nuclear power plants with a large installed capacity. Its differences and advantages are determined by the novelty and uniqueness of production, its goals, technology and equipment. All reactor installations of the BelNPP were intended for pilot industrial confirmation or denial of technical ideas and solutions laid down by designers and constructors, research of technological regimes, structural materials, fuel elements, control and protective systems.

All three power units have no direct analogues either in our country or abroad. They embodied many of the ideas for the future development of nuclear energy:

• power units with industrial-scale channel water-graphite reactors were built and commissioned;
• serial turbo units with high parameters with thermal power cycle efficiency from 36 to 42% were used, which no nuclear power plant in the world has;
• fuel assemblies were used, the design of which excludes the possibility of fragmentation activity entering the coolant even when the fuel rods are destroyed;
• carbon steel is used in the primary circuit of the reactor of the 2nd unit;
• the technology for using and handling liquid metal coolant has been largely mastered;

The Beloyarsk NPP was the first nuclear power plant in Russia to face in practice the need to solve the problem of decommissioning spent reactor plants. The development of this area of ​​activity, which is very relevant for the entire nuclear energy industry, had a long incubation period due to the lack of an organizational and regulatory document base and the unresolved issue of financial support.

The more than 50-year period of operation of the Beloyarsk NPP has three fairly distinct stages, each of which had its own areas of activity, specific difficulties in its implementation, successes and disappointments.

The first stage (from 1964 to the mid-70s) was entirely associated with the launch, development and achievement of the design level of power of the 1st stage power units, a lot of reconstruction work and solving problems associated with imperfect designs of units, technological regimes and ensuring sustainable operation of fuel channels. All this required enormous physical and intellectual efforts from the station staff, which, unfortunately, were not crowned with confidence in the correctness and prospects of choosing uranium-graphite reactors with nuclear superheated steam for the further development of nuclear energy. However, the most significant part of the accumulated operating experience of the 1st stage was taken into account by designers and constructors when creating uranium-graphite reactors of the next generation.

The beginning of the 70s was associated with the choice of a new direction for the further development of the country's nuclear energy - fast neutron reactor plants with the subsequent prospect of building several power units with breeder reactors using mixed uranium-plutonium fuel. When determining the location for the construction of the first pilot industrial unit using fast neutrons, the choice fell on the Beloyarsk NPP. This choice was significantly influenced by the recognition of the ability of the construction teams, installers and plant personnel to properly build this unique power unit and subsequently ensure its reliable operation.

This decision marked the second stage in the development of the Beloyarsk NPP, which for the most part was completed with the decision of the State Commission to accept the completed construction of the power unit with the BN-600 reactor with an “excellent” rating, rarely used in practice.

Ensuring the quality of work at this stage was entrusted to the best specialists from both the construction and installation contractors and the station’s operating personnel. The plant personnel acquired extensive experience in setting up and mastering nuclear power plant equipment, which was actively and fruitfully used during commissioning work at the Chernobyl and Kursk nuclear power plants. Special mention should be made of the Bilibino NPP, where, in addition to commissioning work, an in-depth analysis of the project was carried out, on the basis of which a number of significant improvements were made.

With the commissioning of the third block, the third stage of the station’s existence began, which has been going on for more than 35 years. The goals of this stage were to achieve the design parameters of the unit, confirm in practice the viability of design solutions and gain operating experience for subsequent consideration in the design of a serial unit with a breeder reactor. All these goals have now been successfully achieved.

The safety concepts laid down in the unit design were generally confirmed. Since the boiling point of sodium is almost 300 o C higher than its operating temperature, the BN-600 reactor operates almost without pressure in the reactor vessel, which can be made of highly plastic steel. This virtually eliminates the possibility of rapidly developing cracks. And the three-circuit scheme of heat transfer from the reactor core with an increase in pressure in each subsequent circuit completely eliminates the possibility of radioactive sodium from the 1st circuit getting into the second (non-radioactive) circuit, and even more so into the steam-water third circuit.

Confirmation of the achieved high level of safety and reliability of the BN-600 is the safety analysis performed after the accident at the Chernobyl nuclear power plant, which did not reveal the need for any urgent technical improvements. Statistics on the activation of emergency protections, emergency shutdowns, unplanned reductions in operating power and other failures show that the BN-6OO reactor is at least among the 25% of the best nuclear units in the world.

According to the results of the annual competition, Beloyarsk NPP in 1994, 1995, 1997 and 2001. was awarded the title “Best NPP in Russia”.

Power unit No. 4 with the fast neutron reactor BN-800 is in the pre-startup stage. The new 4th power unit with the BN-800 reactor with a capacity of 880 MW was brought to the minimum controlled power level on June 27, 2014. The power unit is designed to significantly expand the fuel base of nuclear energy and minimize radioactive waste through the organization of a closed nuclear fuel cycle.

The possibility of further expansion of the Beloyarsk NPP with power unit No. 5 with a fast reactor with a capacity of 1200 MW is being considered - the main commercial power unit for serial construction.